THEORY OF UNDRAINED CREEP RUPTURE OF NORMALLY CONSOLIDATED CLAY BASED ON ELASTO-VISCOPLASTICITY

Abstract

A theory of undrained creep rupture of normally consolidated clay is developed within the framework of an elasto-viscoplastic constitutive model. Particular emphasis is placed on giving the analytical expressions whereby all important aspects of undrained creep rupture are clearly explained. The principal expressions derived are as follows : the time-independent failure condition in terms of effective stress; the equation governing the migration of effective stress state during undrained creep; the relationship between rupture life and creep stress; the equation governing the effective stress state at the minimum creep rate; and the deviatoric creep equations governing the time-dependent variations of deviatoric strain and of deviatoric strain rate in the whole process of creep rupture. The validity of the creep rupture theory is successfully verified based on the results of undrained triaxial creep tests on isotropically, normally consolidated samples of a natural clay.Furthermore, the possible influence of anisotropic consolidation history on the subsequent, undrained creep rupture behavior is concisely indicated.